Is it possible to tell if WSAStartup has been called in a process?
Solution 1
Yes it is possible.
And here is how it's done.
bool WinsockInitialized()
{
SOCKET s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
if (s == INVALID_SOCKET){
return false;
}
closesocket(s);
return true;
}
int main()
{
//...
if ( !WinsockInitialized() )
// Init winsock here...
// Carry on as normal.
// ...
}
But it's not really necessary to do this. It's quite safe to call WSAStartup at any time. It's also safe to end each successful call to WSAStartup() with a matching call to WSACleanup().
e.g.
// socket calls here would be an error, not initialized
WSAStartup(...)
// socket calls here OK
WSAStartup(...)
// more socket calls OK
WSACleanup()
// socket calls OK
WSACleanup()
// more socket calls error, not initialized
Solution 2
No, it is not possible to tell if
WSAStartup()
has already been called.Yes,
WSAStartup()
can be called multiple times in a single process, as long as the requested version is supported by the WinSock DLL. Calls toWSAStartup()
andWSACleanup()
must be balanced.WinSock initialization is a negotiated process; you are responsible for validating the info that
WSAStartup()
returns to make sure it meets your app's requirements.Existing sockets are not affected by subsequent
WSAStartup()
calls.Multiple sockets using different WinSock versions is allowed.
See the WSAStartup()
documentation for more information.
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hookenz
Updated on April 17, 2022Comments
-
hookenz about 2 years
I've started writing an ActiveX control that makes use of sockets.
Applications that use this control may or may not also use sockets. Is it possible for my control to tell whether WSAStartup has been called?
If not, call it. A little test reveals that calling WSAStartup multiple times is tollerated. But what happens if a different winsock version is requested? will this break other parts of the application?
-
hookenz over 14 yearsIn addition to this, I've found that so long as the number of WSACleanup calls match the number of successful WSAStartup calls then calling WSACleanup will not affect other socket calls. Provided of course you don't call WSACleanup too many times.
-
czz almost 9 yearsIt's NOT safe to call WSAStartup at any time. From MSDN: "The WSAStartup function typically leads to protocol-specific helper DLLs being loaded. As a result, the WSAStartup function should not be called from the DllMain function in a application DLL. This can potentially cause deadlocks"
-
Remy Lebeau about 7 years
WinsockInitialized()
is returning true instead of false ifsocket()
fails for any error code other thanWSANOTINITIALISED
(MSDN shows 13 possible error codes thatsocket()
could fail with). TheWSAGetLastError()
check is redundant anyway, sincesocket()
either succeeds or fails, checking the error code won't change the result.bool WinsockInitialized() { SOCKET s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); if (s == INVALID_SOCKET) return false; closesocket(s); return true; }